Grease or line the 9”x9” baking pan or line with parchment paper.
Sift the flour and salt together into a bowl and set aside. Sift the powdered sugar in a separate bowl and set aside.
Cream the softened butter in a large bowl or in your stand mixer, on high speed, until it is light and fluffy, about 3 to 5 minutes. Next, add in your vanilla and beat for an additional minute. Gradually add the sifted powdered sugar, mixing slowly until the butter and sugar are combined and appear pale and fluffy. Next, add in the sifted flour and salt and mix on low speed until the dough comes together. It should be a crumbly mixture.
Move the dough from the mixing bowl to your prepared baking pan. Gently press down in an even layer, using either your fingers or a bench scraper. The dough should be about ½ “ thick. Place the dough in the fridge to chill for at least 30 minutes, but if you have time, up to 60 minutes. While the dough is chilling, preheat the oven to 300°F.
Once the dough has chilled, score the dough into rectangles, which are roughly 3” long by 1 ½ “ wide, while it is still in the pan and uncooked. This will make cutting the cookies after baking much easier and cleaner. Also, poke each cookie with a fork 2 to 3 times. This will help to the steam escape and prevent the cookies from bubbling while cooking.
Bake for 50 to 60 minutes, or until the edges are lightly golden brown and the middle is firm. The exact time may vary based on your pan size and oven.
Cool the shortbread completely in the pan before re-slicing and serving.
Storage Instructions: Store your shortbread in an airtight container at room temperature for up to 5 days. For longer storage, freeze the baked cookies for up to 3 months. Just let the cookies thaw at room temperature to enjoy them at a later day.